Adaptive high-beam assist
Here you will find useful information and handy tips relating to the high-beam assistant in the vehicle headlamp.
Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.
As a further development of the AFS system with static light distribution, this system is combined with a camera and suitable image processing. A first step in this direction is the adaptive cut-off line:
with the help of a camera on the windshield, oncoming vehicles and vehicles in front are detected, and the headlamps are controlled in such a way that the light beam ends in front of the other vehicles. In this way, the range of the low beam can be increased from approx. 65 m at present to up to 200 m (3 lux line). If the road is clear, the system switches to high beam, so that the driver has an optimal view at all times. In addition, the vertical angle data of objects within the camera's field of view can provide information about the road topography, so that the illumination can be improved in an area with high and low areas. The adjustment of the possible headlamp range is based on controlling the dazzle levels for other road users. This avoids irritating glare, and at the same time offers the maximum low beam light distribution.
The principle is simple: Driving with the high beam permanently on.
The conventional low beam represents a compromise. It is designed to minimise glare for other road users, but also provide drivers with the best possible illumination of the road. However, at high speeds and on uneven roads, the illumination provided by a conventional low beam is frequently less than ideal.
The so-called "glare-free high beam" follows the principle of a high beam that is permanently switched on without the driver having to worry about not being able to react quickly enough to oncoming traffic or dazzling oncoming drivers.
A camera on the windshield inside the vehicle detects the lights of oncoming vehicles and vehicles in front up to a distance of 850 m (depending on the vehicle manufacturer). The camera is capable, in combination with evaluation electronics, of recording and evaluating many visual aspects of the traffic conditions and identifying dangers in order to react to changes in the conditions.
The headlamps are controlled based on the image data from the camera, so that road users who are in danger of being dazzled are automatically excluded from the high beam distribution. This produces a "light tunnel" where the detected vehicle remains in the dark and the light intensity is no higher than one lux. This tunnel can even track the detected vehicle dynamically and its dimensions can be varied. The area directly in front of the vehicle is permanently illuminated by a light distribution which is similar to the low beam.
Using the camera data and intelligent headlamp control, the light distribution adjusts automatically to the traffic situation so that the high beam distribution remains available to the driver, thus significantly increasing the visual range compared to the normal low beam. Sources of danger are therefore identified in good time and accidents avoided.
There are very different variants of maintenance work for high beams with integrated assistance systems. Depending on the manufacturer and model, classic high beam systems are adjusted together with the low beam, or separately in accordance with the manufacturer's instructions. New ultra-modern headlamp systems are adjusted in conjunction with the relevant control unit using diagnostic units.
Depending on the manufacturer, vehicles equipped with a high-beam assistant must be dealt with separately. With several manufacturers, the glare-free high beam is adjusted together with the low beam. The system is only checked in the event of complaints by customers. With other manufacturers, checking/adjustment is mandatory. Before carrying out the high beam assist adjustment, the vehicle should be prepared in accordance with the statutory regulations (correct tire pressure and loading, etc.) and the manufacturer's instructions. To perform the subsequent adjustment of the vertical cut-off line, the headlamp modules must be in the basic setting. This can be achieved using a diagnostic tester. A special aiming screen in an analog beamsetter is required for several high beam assistance systems. The SEG IV series by Hella Gutmann Solutions is equipped with this kind of aiming screen.
During this procedure, the headlamp modules are moved into a specific position and the vertical cut-off line is activated, as in the graphic which shows the headlamp on the left as an example.
The vertical line of the light distribution (orange arrow) must now be precisely adjusted with reference to the center line, or the zero line of the aiming screen. The new setting is then stored as the normal position. In the case of the vertical cut-off line, correct adjustment is absolutely essential as otherwise other road users may be exposed to extreme glare. The adjustment of the headlamp on the right is to be performed mirror-inverted.
Headlamps also exist in which adjusting screws for adjustment of the high beam distribution are no longer available. This is the case with the new Audi A8 with Matrix Beam headlamps, for example.
The heart of the Matrix LED headlamp is a glare-free high beam which has been implemented using a non-mechanical system. This allows the driver to travel in their vehicle with a permanent high beam without risk of dazzling oncoming traffic or any vehicles in front. A camera detects oncoming traffic and traffic in front, and individual LEDs are then switched off or dimmed within fractions of a second to exclude these vehicles from the field of high beam light distribution. The use of Matrix technology allows, for the first time, several "tunnels" to open simultaneously. One example of this is the scenario where several oncoming vehicles are driving one behind the other. While these are "shielded", the high beam continues to illuminate all the areas between the vehicles and to the left and right of them at full power. As soon as no vehicle is in the driver’s field of vision any longer, the system reverts to full high beam lighting. In addition to specifically shielding other vehicles, the light cone of the Matrix high beam also adapts to the driving situation, for instance in the case of negotiating bends when the cornering light function is required. In such a situation, the intensity of the light cone can be varied at the side or focused on the middle of the road by controlling the LEDs in different ways. Consequently the driver’s visibility at night improves dramatically while, at the same time, the risk of subjecting oncoming traffic to glare is eliminated.
With this headlamp system, 25 individual LEDs perform the task of distributing the high beam. Each of these LEDs can be switched on or off separately. A diagnostic tester is also required to check or adjust the light distribution of this headlamp system. Once the vehicle has been prepared, a single LED, referred to as the "Master LED", is switched on using the diagnostic tester. The evaluation is carried out based on the position of the light distribution. Figure 1 shows the correct position of the inner cut-off line on the zero line of the aiming screen. If it deviates from this position (Figure 2), the correction value (distance from the zero line) must be transferred to the relevant control unit via a diagnostic tester. The figures show the headlamp on the left. The evaluation of the headlamp on the right is to be performed mirror-inverted.
This light-specific phenomenon is a frequently recurring theme which is dealt with in various reports. But what exactly causes it? The "blue edge" refers to the light component in the area of the cut-off line which frequently has a bluish white light colour.
The characteristic and intensity of the edge depends on several factors. Here are some examples:
1. Lens material of projection module
The light refraction or diffusion varies depending on the material of the focusing lens, which can be glass, polymethylmethacrylate, or polycarbonate, for example. This affects the light colour.
2. Position of the light source in relation to the bulb shield
Light sources are mounted at different distances and positions (vertically) in relation to the bulb shield. Light is therefore "refracted" or "diffracted" differently at the bulb shield.
3. Reflector or projector-type system
The way in which light is emitted or focused also has an effect on the cut-off line. The blue edge of a reflector-type system is normally not as pronounced as that of a projector-type system. The reason for this is the so-called "degree of hardness". This refers to the light-to-dark transition (cut-off line). Projector-type systems have a higher degree of hardness due to the bulb shield.
Several important points must be observed when checking and adjusting the light distribution of modern headlamps. The adjustment can only be made correctly if the light distribution is interpreted correctly. It is therefore always extremely important for the person(s) performing the adjustment to have the necessary expertise. The specifications of the manufacturer for high beam assistance systems in particular must be observed. Compliance with the tolerances in relation to the standing surface of the vehicle and the beamsetter is also essential. Last but not least, the necessary equipment also plays a significant role as modern lighting systems can only be checked and adjusted correctly by using the diagnostic tester and a suitable beamsetter.